feat: implement in-process-flagd provider

[bacherfl]

This PR adds the in-process flagd provider, following the flagd specification

[odubajDT]

Nice work! :)

[Kavindu-Dodan]

@bacherfl I think you forgot to include the go.mod file.

Given this is a new module, we need to configure release please configuration ¹ and set manifest ² with initial release version.

Regarding module name 🤔 shall we prefix this with flagd (flagd-in-memory). This should help the folder ordering in provider directory ³ and give the idea that this is a flagd module.

Also, I faced a weird depdency issue with flagd. This was due to OTel dependency issue. Please use the latest flagd core version - https://github.com/open-feature/flagd/releases/tag/core%2Fv0.6.5

Footnotes

1. https://github.com/open-feature/go-sdk-contrib/blob/main/release-please-config.json ↩

2. https://github.com/open-feature/go-sdk-contrib/blob/main/.release-please-manifest.json ↩

3. https://github.com/open-feature/go-sdk-contrib/tree/main/providers ↩

[toddbaert]

Approved pending comment here. I'll add the test suite once this is merged and then we can consider what we'd want before a final release (we may want spec 0.7.0 implemented first).